Investigating numerosity discrimination in the domestic dog using awake, unrestrained fMRI Open Access

Chiu, Veronica (Spring 2019)

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Numerosity, or number representation without use of symbols, is a highly conserved across a variety of animals. Numerosity allows for quick, imprecise quantity judgements across stimulus modalities. Although number representation in humans and non-human primates has been well-studied, numerosity studies in other animals have only utilized behavioral paradigms. Particularly in dogs, these past behavioral tests have not provided strong evidence for innate number representation. The present study investigated neural activation in the canine cortex in response to changes in numerosity using awake, unrestrained fMRI. Eleven awake, unrestrained dogs passively viewed alternating dot arrays of 2 vs 10, 4 vs 8, or 6 vs 6 dots in a block fMRI design. After preprocessing, the data were split into two unique datasets to localize a region and test for a linear response to the ratios of 1, 2, or 5. In eight of the eleven dogs, we identified regions in the parietal cortex that were differentially active to the modulated effect of numerosity, which were replicable in an independent dataset at p = 0.04. These regions, although variable in location, were consistent with previous findings that had implicated the parietal cortex in encoding numerosity. To our knowledge, this study is the first to provide evidence of an untrained canine ability to discriminate changes in numerosity.

Table of Contents

Table of Contents

Introduction 1

Defining Numerosity 1

Detecting Numerical Change 2

Proposed Number Systems 2

Evidence for Numerosity 4

a. Human Studies 4

b. Nonhuman Primate Studies 6

c. Non-Primate and Domestic Dog Studies 7

Numerosity-Specific Regions in the Brain 8

Purpose and Hypothesis 9

Methods 10

Participants 10

MRI Scan Acquisition 11

Experimental design 11

Preprocessing 12

Analysis 13

Results 15

Discussion 17

References 24

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